1. Field of the Invention
The field of the invention comprises low dielectric constant nanocomposite materials for use in the semiconductor industry. Specifically, the invention relates to composites containing an oxide such as SiO2 and an organic polymer, such as a poly(chloro-para-xylylene) (PPXC).
2. Discussion of the Related Art
As semiconductor device density increases to permit faster computer operations, the demands on dielectric materials used in semiconductor manufacture becomes greater. The dielectric materials must be good insulators, i.e., must possess high dielectric strength and must possess a low dielectric constant (K). Additionally, as device density increases, the dielectric materials should have sufficient mechanical strength to withstand subsequent processing steps of manufacture, including chemical mechanical polishing. Additionally, the dielectric materials should have sufficient thermal stability to withstand subsequent processing steps and long-term operation at elevated temperatures.
Currently, SiO2 is the most commonly used dielectric material. SiO2 has sufficient mechanical strength and thermal stability. However, SiO2 has a relatively high dielectric constant (K=3.9-4.3) and thus, is not ideally suited for the demand of low dielectric constant high performance sub-0.35 micron semiconductor technologies.
More recently, organic polymeric materials have been proposed for use as dielectric materials in semiconductor manufacturing. Organic polymers include poly(para-xylylenes), or PPX, among others. These organic materials have a lower dielectric constant than SiO2, but have insufficient mechanical strength and thermal stabilities to meet the rigorous demands of semiconductor manufacture.
To provide advantages of both types of dielectric materials, nanocomposite structures have been proposed for use in the semiconductor industry. Nanocomposites of this invention are thin film materials characterized by the existence of mixtures of individual domains of dielectric materials, each being in the size range of from about 20 xc3x85 to about 200 nm.
Several methods have been proposed to synthesize nanocomposite and intercalative layered structures and the different polymer and ceramic constituents in these composites. One currently available process for manufacturing nanocomposite materials utilizes sol-gel methods {Mattes et al., U.S. Pat. No. 5,420,081, herein incorporated fully by reference. Another method utilizes sputtering methods {Holtz et al., U.S. Pat. No. 5,158,933, herein incorporated fully by reference}. {Gonsalves et al., Mat. Res. Soc. Symp. Proc. 435:55-65 (1996)}. Using these methods a chemical link is formed between the ceramic and organic phases and therefore may produce desired properties in the bulk nanocomposite or nanocomposite coating.
However, a chemical bond between ceramic and organic phases is not a prerequisite for enhanced material properties, especially when interpenetrating phases are present on the order of the nanometer size range. At the size of the crystallites within a nanophase structure, molecular interactions may take place which affect the large scale properties of the films. Nanocomposites which are made by solution or melt-based methods rely on good thermodynamic mixing or molecular dispersion to make effective nanoscale blends.
However, the solution-based and sol-gel based processes are not well suited for the manufacture of semiconductors with sub-micron feature sizes. With device features of 0.35 xcexcm and less, the thickness and conformality of the dielectric layers must be very carefully controlled, and the compositions of each phase must be reproducible. Bulk mixing of components is unsatisfactory for achieving this aim.
Additionally, sputtering, conventional thermal CVD, and plasma enhanced chemical vapor deposition (PECVD) methods can be used to co-deposit dielectric materials. However, they are poorly suited for depositing nanocomposites with widely different physical properties because deposition conditions may be very different for each material in the composite. For example, the typical CVD deposition of SiO2 occurs at high temperatures (above 350xc2x0 C.), whereas deposition of organic polymers such as poly(para-xylylenes) can take place at temperatures well below 100xc2x0 C. Therefore, current manufacturing methods do not permit the deposition of dielectric materials as thin films of differing physical and chemical properties.
So far, however, no CVD method has been developed to synthesize nanocomposite thin film materials. The lack of these methods has inhibited the use of nanocomposite materials for thin film applications, especially those related to the electronics industry. Therefore, new methods are needed for accurately and reproducibly producing thin film nanocomposites for semiconductor manufacturing.
Thus, one object of the invention is the development of methods for manufacturing nanocomposite thin films with low dielectric constant, high dielectric strength, high thermal stability, and high mechanical strength.
Another object of the invention is to provide methods for the co-deposition of different semiconductor materials which have different physical and chemical properties.
A further object of the invention is to provide semiconductor device thin films comprising nanocomposites made by co-depositing dielectric materials.
An additional object of the invention is the manufacture of nanocomposites comprising organic co-polymers.
A further object of the invention is the manufacture of nanocomposites comprising cross-linked oxide and organic polymers.
Another object of the invention is the manufacture of nanocomposites at near or below room temperatures using chemical vapor deposition.
Yet another object of the invention is to manufacture graded films of oxide and organic polymeric dielectric materials of varying ratios.
Another object of the invention is the manufacture of semiconductor wafers comprised of nanocomposites deposited by chemical vapor deposition.
A further object of the invention is the manufacture of semiconductor devices with nanocomposite thin films deposited by chemical vapor deposition.
According to the invention, new methods are disclosed which can be used to deposit novel semiconductor thin films in the form of nanocomposites using chemical vapor deposition of oxide and organic polymer materials which co-deposit to form the thin film.
Thus, one aspect of the invention is an apparatus for co-depositing different dielectric materials simultaneously.
Another aspect of the invention is the co-deposition of oxide and organic polymeric dielectric materials to form nanocomposites.
An additional aspect of the invention is the deposition of nanocomposite thin films with low dielectric constant, high dielectric strength, high thermal stability and high mechanical strength.
Another aspect of the invention is the deposition of nanocomposite dielectric materials as semiconductor device thin films.
An additional aspect of the invention is the manufacture of nanocomposites comprising organic co-polymers.
A further aspect of the invention is the manufacture of nanocomposites comprising cross-linked oxide and organic polymers.
Yet another aspect of the invention is to manufacture gradient films of oxide and organic polymeric dielectric materials of varying ratios.